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Careful monitoring of insects in soybean fields and assessing how much threat they pose to crop yield could result in fewer insecticide applications and greater cost savings, says Angus Catchot, associate Extension professor of entomology and plant pathology at Mississippi State University.

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Controlling soybean bean leaf beetles

Bean leaf beetles are still an ongoing challenge, Catchot says.

“We’ve been working with this pest a long time; in the Delta, since 2005, we’ve had a problem getting control with pyrethroids. When bifenthrin came on the market, it did a good job of control at the high rates when the other pyrethroids alone were not providing adequate control. Last year, I think we started seeing the edge we had with straight bifenthrin start disappearing — probably because we’ve applied it to such tremendous acreages that we’ve selected to the point it no longer has a clear edge.

“To control bean leaf beetles in the Delta region of the state, I think we’re probably going to have to go to a pyrethroid mixture with acephate. We’re seeing better control of bean leaf beetles with a half-pound of acephate mixed with pyrethroids, or with straight acephate alone at the high rates. Also, there are older materials that still work; Sevin XLR, for example, is very effective, or Larvin.

“In the hills pyrethroids still work well — it’s in the Delta where we’re having problems. For Delta growers, I wouldn’t even consider a straight pyrethroid, but would go with a mix right out of the gate, or a premixed product with multiple modes of action.

“If you have a bad infestation, try to go back two or three days later and assess how the application is working. A lot of times, if you’re only checking fields weekly, it may look like you got zero control, when in fact at two or three days you may have had 80 percent control. But after a week, they’re moving back in, there isn’t enough residual to control the new populations moving in, and it may look like a complete failure, particularly in late July and August.”